Dyes of formula (I) below are described. The dyes are useful as mid-green sensitizing dyes for photographic materials ##STR1## In the above formula, R1 and R3 are methyl or ethyl, at least one of R1 and R3 being methyl. R2 and R4 are substituted or unsubstituted C.sub.1 to C.sub.6 alkyl, provided that R2 and R4 are not both methyl. X1, X2, X3, and X4 are each independently methyl, methylthio, fluoro-substituted methyl or methylthio, or hydrogen, provided that at least one of X1 and X2 and at least one of X3 and X4 are not hydrogen. Y represents an ion as needed to balance the charge of the molecule. The dyes of formula (I) sensitize silver halide to light in the mid-green region of the spectrum.